Spacecraft for communications and broadcast services can operate in geosynchronous orbit to communicate with a ground device (user terminal) by way of a forward user downlink/return user uplink beam that communicatively couples the user terminal and the spacecraft. The positioning, or pointing, of the forward user downlink/return user uplink beam can drift over time, for example, due to temperature changes on the spacecraft, drifts in orbit, etc.
Transmit Antenna Pointing is a technique in which the antenna beam formed on the satellite and pointing to the ground is adjusted to compensate for satellite drifts that occur over time. This adjustment is made by measuring the drift in satellite orientation in some fashion, such as by receiving a beacon from the ground and estimating from that the presumed pointing error in the transmit beams and mechanically correcting the transmit pointing by moving the transmit antenna.
Beamforming is a technique in which a phased array antenna is configured to position the forward user downlink/return user uplink beam such that it is optimized in data capacity at a specific location of the ground device. Beamforming coefficients can be used to adjust the forward user downlink/return user uplink beam's phase and amplitude at the phased array transmitter/receiver to change the pointing of the beam to account for satellite drift, and therefore, increase the data capacity of the user signals. However, using beamforming to adjust pointing by determining the beamforming coefficients on the satellite can be computationally prohibitive. Additionally, implementing the beamforming coefficient determination system on the spacecraft can increase its cost and weight.
Thus, an improved system for determining beamforming coefficients to correct for pointing errors is desired.